Thanks guys for your input. I try to supply w/ more info - English is not my native language but I try my best. Idle has been adjusted to 1100 rpm but it varies slightly. I do not believe that there could be any leak in carb boots, because then the idle would rush and stay at +2000 rpm. The throttle has been adjusted to have 2-3 mm slack. The previous plugs were iridiums and all had a beautiful tan colour - the present plugs are standard plugs. The muffler (brand name Ixil) has all the stuff still inside. KleenAir and float boal vent systems are stock, and judging by the near-mint appearance of the bike, I would assume that the previous owners have not been "performance oriented" (= possibly no mods in the carbs either). When I engage the choke while riding, the throttle is closed and the bike is coasting in gear (hope I have understood "coasting" properly). Have not tried how the bike responds to opening the throttle w/ the choke opened. I have just added some Super Gas Cleaner to the tank - I'll let you know if it has any effect. I suspect that there might be clogging inside the carb(s).

 

Had a ride of 40 km. I tried to open the throttle while the choke was wide open, but then the bike would quickly accelerate to such an rpm level where the problem does not exist. However, the acceleration was very smooth.

 

Mmmmm, aftermarket pipe, no other changes. Runs fine (no hiccups like "bad gas," good plug color) when choke is partially opened and engine is warm. I DOUBT the fuel cleaner will do much to improve things. If all of the plugs have good, consistent color, smooth acceleration on choke,.... I'm not feeling any "clogging in the carbs." I might wonder about needing to rejet just a smidge for the aftermarket pipe?
Any thoughts, Drag??

 

hey guys.. i just got this 96 zx9r cheap and i am having some truble with it and was hopping someone could help me with it.. first is the carbs or something.. when i start the bike it fires right up, idles right, and will take off like it should. but at the top of every gear i get a sputter , then it will either die or drop the rmp's like crazy. i have to hold it wide open to keep it running.. i check the tank and someone coated it and not the right way so i bought a new one... check the fuel pump, it's working like it should. so moved to the carbs. cleaned them three time and it is doing the same thing... i just did it today again because i want to ride.. went down the road. first was fine second started with the sputter.. then it died and had nothing. lights, starter, nothing.. i remembered the last time it was a fues. well it was again, the main fues in the silonoid.. can anyone help me fix my bike. i'm dieing over here and i ready to dig a hole and throw it in it..... it does have a after market pipe and the guy said it was jetted.. and the jet holes are huge... should i get a smaller jet or biger? i keep killing plugs too.... help... thank you guys for looking and god bless.
zx-9er

 

Managed to sync the carbs, which were quite severely out of sync. At the same I opened the pilot screws 1/4 turn in each carb. Now the engine idles a little more evenly but no improvement in the sputtering issue at low throttle opening.

 

I am still thinking the emulsifier tubes being partially clogged and the carb sych even though adjusted right now, will need double checked to make sure. (Basically, anytime the rack is removed, just place the gauges on to double check.) The reason being....the same symptoms caused me a nice low side crash at my local track because of the stuttering and throttle wandering during a wet weather race in 1990.

 

I don't think that the emulsifier tubes could have anything to do with the problem, since the symptoms occur below 1/10th throttle opening and the needle jets come into play later at greater throttle openings.

I have learned that the throttle cable does not directly lift the slides but instead turns the butterflies hence adjusting the vacuum to the slides. Now if there are even minute differences in the friction on the slide surfaces, this would result in uneven opening of the slides even though the butterflies are in sync. Does this make sense? Are the great (here good is not enough) instructions available how to dismantle and clean the carb interiors?

 

Hey Riik, did you get things sorted out?

 

Well....nope. The carb cleaner in the gas does not seem to improve. The next step will be to clean the carbs. I've found a great deal of info on carbs, and I'm pretty convinced that the culprit is in the pilot system. After cleaning I'll have to start tampering the pilot screw adjustments.
Before the carb cleaning I'll run the engine below 1/10th throttle for a minute and check the plugs.

 

Another good carb read if you do not have it.

Carburador Keihin CVK40: The Care & Feeding. (Redondo Ron) « El blog de Jotuna